Machining stations as mentioned before are used, for example, in transfer lines. In transfer lines a plurality of machinings, which are often complex, are carried out on workpieces. For that a plurality of machining stations, in particular for metal cutting machining, are arranged one behind the other and connected to each other by a conveying line. A few machining steps are carried out by the machining station, however, the plurality of the machining stations, one arranged behind the other, allow a varied and also complex machining of the workpiece.
Of course, here a highly exact positioning of the workpiece with regard to the machining unit, respectively the tool head or the tool spindle, is essential.
The state of the art therefore knows so-called translators or a topside transfer which remove the workpiece from the conveying line and put it down on a machining point.
Thus, for example, the German patent specification 44 22 416 shows a machining center where the workpiece is clamped on a workpiece carrier. The workpiece carrier can be moved into a workpiece changing station where a workpiece change is carried out. This workpiece changing station is located away from the machining unit that means not in the direct range of the machining spindle. The workpiece carrier can be lowered here along a vertical axis (Y-axis) in order to take up the workpiece in the changing station. Furthermore the workpiece carrier can be moved horizontally (in Z-direction) in order to move the workpiece towards the tool spindle. Furthermore it is provided, according to this state of the art, that the workpiece can be rotated around a vertical axis (B-axis).
It is a disadvantage in this state of the art that the construction for the two linear axes and the one rotational axis of the workpiece is very large. The two linear axes in Y- and Z-direction are designed as compound rests and need, for a sufficiently high positioning accuracy, an appropriate effort, leading to heavy masses (and thus to large drives and high expenses). It has to be taken into consideration here that, for example, on the arrangement designed as a portal also the vertical rotational axis of the workpiece in the workpiece carrier has to be taken care of.
Besides the very high expenses, this arrangement is not suited, either, to reach a high efficiency because the workpiece carrier has to be removed from the machining room, that means from the range of the machining spindle, in order to put down a machined workpiece on a remote workpiece changing point and to pick up a new workpiece.
A similar suggestion also shows the utility model 298 15 125. In this device, too, the workpiece is offered on a workpiece discharge point to a workpiece holding device which can move along at least two axes X and Z which feeds it a plurality of machining stations arranged one behind the other.